Fix pane border overflow

internal/tui/update.go

@@ -42,9 +42,27 @@ func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case tea.WindowSizeMsg:
 		m.width = msg.Width
 		m.height = msg.Height - 1
-		m.list.SetSize(msg.Width/2, m.height)
-		m.detail.Width = msg.Width - msg.Width/2
-		m.detail.Height = m.height
+
+		leftWidth := msg.Width / 2
+		rightWidth := msg.Width - leftWidth
+		leftHeight := m.height
+		rightHeight := m.height
+
+		if m.focus == listPane {
+			leftWidth -= 2
+			leftHeight -= 2
+		} else {
+			rightWidth -= 2
+			rightHeight -= 2
+		}
+
+		leftWidth -= 2
+		rightWidth -= 2
+
+		m.list.SetSize(leftWidth, leftHeight)
+		m.detail.Width = rightWidth
+		m.detail.Height = rightHeight
+
 		if m.focus == listPane {
 			m.list, cmd = m.list.Update(msg)
 		}